热休克蛋白27改善实验性小鼠心力衰竭的机制研究

目的 探讨热休克蛋白27(Hsp27)改善实验性小鼠心力衰竭的机制.方法 (1)心肌损伤诱导:Hsp27转基因鼠(TG)和作为对照组的野生型鼠(WT),分别腹腔注射阿霉素(25 mg/kg)或生理盐水.(2)组织学检杳:给药后第3天,取心脏石蜡切片并HE染色.在石蜡切片上进行细胞凋亡(TUNEL染色)、心肌细胞、细胞核的三重荧光染色,激光共聚焦显微镜观察.小鼠死亡后,观察胸腔、腹腔有无积液,取心和肺进行石蜡切片和HE染色.(3)线粒体超微结构:给药后第3天,取左心室肌制超薄切片,在电镜下观察.(4)蛋白质氧化修饰测定:给药后第3天取心脏,进行抗DNP免疫印迹分析.结果 尸检结果:死亡小鼠均出现明显的胸腔积液和腹腔积液,肺泡中出现红细胞渗出和肺泡塌陷,WT和TG鼠心肌细胞空泡变性,WT鼠心肌出现纤维化,而TG鼠心肌没有相应变化.阿霉素给药后第3天:WT和TG鼠心肌细胞凋亡都显著增加,但与WT鼠心肌相比,TG鼠的心肌细胞凋亡则被显著抑制;WT和TG鼠心肌的羰基化显著增加,但与阿霉素-WT鼠心肌相比较,阿霉素-TG鼠心肌的羰基化反应被显著抑制;WT和TG鼠心肌细胞中出现了几种线粒体的结构改变如电子密度增加,嵴肿胀、模糊和消失,但这些改变在WT鼠心肌中要比TG鼠中严重.结论 线粒体相关的氧化应激和细胞凋亡可能参与了Hsp27对阿霉素诱导心力衰竭的保护作用.     

热休克蛋白27对小鼠实验性心力衰竭的保护作用

目的 观察热休克蛋白27（Hsp27）心肌特异性高表达对doxorubicin（Dox）诱导的慢性心力衰竭（心衰）小鼠的影响。方法 （1）建立心肌特异性高表达Hsp27的转基因鼠模型;（2）经Dox诱导小鼠的慢性心衰,并观察Hsp27对小鼠生存率、左心室血流动力学的影响。结果 （1）成功建立心肌特异性过表达Hsp27的转基因鼠模型;（2）Hsp27心肌特异性过表达显著改善了Dox诱导的小鼠死亡率（P〈0．01）和左心室血流动力学参数变化（P〈0．05或P〈0．01）;（3）Hsp27表达显著抑制了Dox诱导的心肌氧化应激。结论 Hsp27心肌特异性过表达对Dox诱导的小鼠心衰具有显著的抑制作用。     

Bcl-xl reduces doxorubicin-induced myocardial damage but fails to control cardiac gene downregulation

OBJECTIVE: We recently reported that doxorubicin (Dox), an effective anti-cancer drug, induces apoptosis in cardiac myocytes in association with reduction of Bcl-xl expression. In the present study, we further examined whether overexpression of Bcl-xl ameliorates Dox-induced cardiac myocyte damage. METHODS AND RESULTS: Overexpression of the Bcl-xl gene by adenovirus vector resulted in an 11-fold increase in Bcl-xl protein in neonatal rat cardiac myocytes (BCL) compared to that in cells with beta-galactosidase gene transfection (CTL). Although Dox treatment generated similar amounts of reactive oxygen species (ROS) in BCL and CTL, cell viability was maintained and the number of apoptotic cardiac myocytes was significantly decreased in BCL. Cytochrome c release and enhanced caspase-3 activity after Dox treatment were significantly suppressed and Bax expression level was decreased in BCL. Cardiac-specific gene expression is known to be inhibited by Dox. The expression of cardiac alpha-actin and sarcoplasmic reticulum Ca(2+)-ATPase 2a mRNA was equally inhibited in BCL and CTL after Dox treatment. CONCLUSIONS: Overexpression of Bcl-xl in cardiac myocytes failed to regulate Dox-induced ROS generation and cardiac-specific gene downregulation but inhibited apoptosis accompanied by reduction of Bax protein.     

Grape Seed and Skin Extract Protects Against Acute Chemotherapy Toxicity induced by Doxorubicin in Rat Heart

Doxorubicin (Dox), an antitumor anthracycline antibiotic, plays a key role in the treatment of many neoplastic diseases. However, its chronic administration induces cardiomyopathy. Increased oxidative stress is a major factor implicated in Dox-induced cardiotoxicity. We hypothesized that a pre-treatment with grape seed and skin extract (GSE), commonly used as an antioxidant agent, may alleviate this cardiotoxicity. Rats were treated with GSE (500 mg/kg bw) by intraperitoneal injection during 8 days. On the 4th day, rats were administered a single dose of Dox (20 mg/kg). At the end of the treatment, their hearts were Langendorff-perfused, subjected to ischemia/reperfusion (I/R) injury, and left ventricular functions as heart rate and developed pressure measured. Hearts were also used to determine free iron, H2O2, Ca2+, lipoperoxidation, carbonylation and antioxidant enzymes such as superoxide dismutase (SOD), catalase and peroxidase. Doxorubicin drastically affected heart activity as evidenced after I/R experiments. This effect was associated with an increase in heart free iron and a decrease in Ca2+ concentrations. This effect may have contributed to oxidative stress as assessed by high lipoperoxidation and carbonylation level. GSE counteracted Dox-induced disturbances of hemodynamic parameters, alleviated oxidative stress as assessed by normalized iron and Ca2+ levels and increased SOD activity especially the Mn isoform.     

Toll样受体4在血管紧张素Ⅱ致高血压小鼠心脏纤维化中的作用

目的探讨Toll样受体4(TLR4)在血管紧张素Ⅱ(AngⅡ)所致高血压小鼠心脏纤维化过程中的作用。方法野生型C57小鼠18只分为3组:空白对照组、AngⅡ组和TLR4阻断组,每组6只。AngⅡ组和TLR4阻断组AngⅡ微量泵灌注建立高血压模型,TLR4阻断组尾静脉注射TLR4中和抗体后,小鼠尾动脉套法测血压,心动超声图观察小鼠的心脏功能变化。免疫组织化学、Masson染色观察心脏纤维化。RT-PCR检测心肌白细胞介素1β和单核细胞趋化蛋白1 mRNA表达。结果与AngⅡ组比较,TLR4阻断组小鼠血压降低,左心室舒张末期壁厚度减少,舒缩未期左心室内径增加(P<0.05)。心肌组织半乳糖凝集素2阳性巨噬细胞浸润减少,白细胞介素1β和单核细胞趋化蛋白1 mRNA表达水平降低(P<0.05)。小鼠心肌间质和血管周围纤维化减轻(P<0.05)。结论 TLR4通过介导炎性反应参与AngⅡ所致高血压小鼠心脏纤维化过程。     

Left-right asymmetric ventricular expression of CARP in the piglet heart: regional response to experimental heart failure

BACKGROUND AND AIM: Cardiac ankyrin repeat protein (CARP), whose expression is down-regulated in response to doxorubicin (Dox) in vitro, has been proposed to be a marker of experimentally-induced cardiac hypertrophy in rodent models. In piglets, the rapid hypertrophy rate of the left ventricle (LV) as compared to that of the right ventricle (RV) represents a natural model of asymmetric ventricular enlargement. We tested whether CARP expression correlates with postnatal ventricular hypertrophy and to what extent CARP can be sensitive to Dox treatment in vivo. METHODS: CARP mRNA and protein levels were quantified (by Northern blot hybridization, semi-quantitative RT-PCR and Western blot) in the piglet heart, both during early postnatal development and upon Dox-induced cardiomyopathy (Dox-CM). RESULTS: The study revealed: (1) significantly augmented CARP mRNA and protein levels in the LV compared to the RV resulting in left vs. right asymmetry in ventricular CARP expression throughout early postnatal development; (2) dose- and chamber-dependent CARP mRNA and protein enrichment in ventricular myocardium in response to Dox; and (3) abolishment of asymmetric patterns of ventricular CARP expression at heart failure resulting from Dox-CM. CONCLUSIONS: (1) CARP is differentially regulated in the LV and RV during both postnatal development and disease; and (2) monitoring of ventricular CARP expression patterns can be used for further analysis of transition from compensated to overt heart failure.     

Disulfiram/copper complex activated JNK/c-jun pathway and sensitized cytotoxicity of doxorubicin in doxorubicin resistant leukemia HL60 cells

Resistance to chemotherapy and non-specific cytotoxicity are the major challenges to the treatment of acute myeloid leukemia (AML). In this study, we demonstrated that the disulfiram/copper (DS/Cu) complex alone exhibited cytotoxicity to doxorubicin (Dox) resistant leukemia HL60 cells (HL60/Dox) and enhanced cytotoxicity of Dox to HL60/Dox cells. DS/Cu inhibited Bcl-2 expression and enhanced Dox-induced apoptosis. DS/Cu/Dox in combination significantly induced c-Jun expression and JNK and c-Jun phosphorylation. JNK inhibitor Sp600125 attenuated DS/Cu/Dox-induced apoptosis and suppressed DS/Cu/Dox-induced protein expression in JNK/c-jun pathway. This study suggested that DS/Cu complex may re-sensitize HL60/Dox cells to Dox through activating JNK/c-jun as well as inhibiting anti-apoptotic bcl-2 expression.     

Reactive oxygen species regulate FLICE inhibitory protein (FLIP) and susceptibility to Fas-mediated apoptosis in cardiac myocytes

OBJECTIVE: Fas ligand (FasL) is a key cytokine which initiates apoptosis when FasL binds to its receptor, Fas. Cardiac myocytes are generally resistant to Fas-induced apoptosis. However, sublethal dose of doxorubicin (Dox) can sensitize cardiac myocytes to Fas-induced apoptosis. We investigated the molecular mechanism by which Dox sensitizes cardiac myocytes to Fas-induced apoptosis. FLICE inhibitory protein (FLIP) is a key molecule for blocking Fas-induced apoptosis by functioning as a caspase-8 dominant negative. METHODS AND RESULTS: FLIP was constitutively expressed in cultured neonatal rat cardiac myocytes. FLIP protein levels were markedly down-regulated by Dox in a time-dependent and dose-dependent manner. Next, we examined the relation of reactive oxygen species (ROS) by Dox to the expression of FLIP. Both of N-acetylcysteine (NAC) and the combination of superoxide dismutase and catalase restored the decreased FLIP in Dox-treated cardiac myocytes to the basal level. NAC also restored the increased formation of thiobarbituric acid-reactive substance after Dox-treatment. Concurrently, the susceptibility to Fas-mediated apoptosis disappeared with the treatments of the antioxidant agents. Hydrogen peroxide down-regulated FLIP in a dose-dependent fashion and also sensitized cardiac myocytes to Fas-induced apoptosis. CONCLUSIONS: FLIP, an inhibitor of apoptosis induced by cytokines of TNF family, contributes at least partly to Dox-induced sensitization to Fas-mediated apoptosis in cardiac myocytes. The expression of FLIP in cardiac myocytes is regulated by ROS.     

Cardiac ICAM-1 mediates leukocyte-dependent decreased ventricular contractility in endotoxemic mice

OBJECTIVE: Binding of ICAM-1 expressed on cardiomyocytes decreases cardiomyocyte contractility in vitro by altering the intracellular Ca2+ transient. We tested the hypothesis that signaling via ICAM-1 contributes to decreased left ventricular contractility in an in vivo model of systemic inflammation. METHODS: C57B6 wild-type mice and ICAM-1 knock-out mice were treated with intraperitoneal lipopolysaccharide (LPS) then left ventricular contractility was measured 6 h later using a volume-conductance micromanometer catheter. We repeated this experiment in chimeric mice lacking ICAM-1 expression in bone marrow-derived cells (M-) and/or lacking ICAM-1 expression in the heart and other tissues (H-). RESULTS: In C57B6 wild-type mice LPS injection significantly increased cardiac ICAM-1 expression and decreased in vivo measures of left ventricular contractility (end-systolic elastance, Ees decreased 58 +/- 4%, p < 0.05, [dP/dtmax]/EDV decreased 60 +/- 6%, p < 0.05). Cyclophosphamide pretreatment to decrease leukocyte count prevented the LPS-induced decrease in contractility. In ICAM-1 knock-out mice LPS did not decrease any measure of contractility. LPS did not decrease left ventricular contractility in M+/H- mice but decreased contractility in M+/H+ and M-/H+ mice to the same extent as in C57B6 wild-type mice implicating the importance of cardiac ICAM-1. CONCLUSIONS: We conclude that signaling via cardiac ICAM-1 is necessary to mediate leukocyte-dependent decreases of left ventricular contractility in endotoxemic mice.     

α-Enolase plays a catalytically independent role in doxorubicin-induced cardiomyocyte apoptosis and mitochondrial dysfunction

Backgroundα-Enolase is a glycolytic enzyme with “second jobs” beyond its catalytic activity. However, its possible contribution to cardiac dysfunction remains to be determined. The present study aimed to investigate the role of α-enolase in doxorubicin (Dox)-induced cardiomyopathy as well as the underlying mechanisms.Experimental approachesThe expression of α-enolase was detected in rat hearts and primary cultured rat cardiomyocytes with or without Dox administration. An adenovirus carrying short-hairpin interfering RNA targeting α-enolase was constructed and transduced specifically into the heart by intramyocardial injection. Heart function, cell apoptosis and mitochondrial function were measured following Dox administration. In addition, by using gain- and loss-of-function approaches to regulate α-enolase expression in primary cultured rat cardiomyocytes, we investigated the role of endogenous, wide type and catalytically inactive mutant α-enolase in cardiomyocyte apoptosis and ATP generation. Furthermore, the involvement of α-enolase in AMPK phosphorylation was also studied.Key resultsThe mRNA and protein expression of cardiac α-enolase was significantly upregulated by Dox. Genetic silencing of α-enolase in rat hearts and cultured cardiomyocytes attenuated Dox-induced apoptosis and mitochondrial dysfunction. In contrast, overexpression of wide-type or catalytically inactive α-enolase in cardiomyocytes mimicked the detrimental role of Dox in inducing apoptosis and ATP reduction. AMPK dephosphorylation was further demonstrated to be involved in the proapoptotic and ATP-depriving effects of α-enolase.ConclusionOur findings provided the evidence that α-enolase has a catalytically independent role in inducing cardiomyocyte apoptosis and mitochondrial dysfunction, which could be at least partially contributed to the inhibition of AMPK phosphorylation.     

Eicosapentaenoic acid suppresses adverse effects of C-reactive protein overexpression on pressure overload-induced cardiac remodeling

Serum C-reactive protein (CRP) elevation is associated with poor clinical outcome in patients with heart failure (HF). We previously reported that CRP exacerbates the development of pressure overload-induced cardiac remodeling through an enhanced inflammatory response and oxidative stress. In the present study, we examined the effect of eicosapentaenoic acid (EPA), a suppressor of inflammatory response and oxidative stress, on pressure overload-induced cardiac remodeling. Transverse aortic constriction (TAC) was performed on transgenic mice overexpressing CRP (CRPtg) and nontransgenic littermates (TAC/CON). CRPtg with TAC operation were randomly assigned to be fed a standard diet (TAC/CRPtg) or an EPA-enriched diet (7 % of total energy) (TAC/CRPtg/EPA). Myocardial mRNA level of transforming growth factor-β1, proinflammatory cytokines, and oxidative stress markers were increased in TAC/CRPtg in comparison with TAC/CON 1 and 4 weeks after the operation. These parameters were significantly suppressed in TAC/CRPtg/EPA compared with TAC/CRPtg. In addition, after 4 weeks of EPA treatment, as compared with TAC/CRPtg, TAC/CRPtg/EPA mice demonstrated reduced heart and lung weights, increased left ventricular fractional shortening, and decreased left ventricular end-diastolic pressure, together with decreased cardiac hypertrophy, fibrosis, and improved cardiac function. In conclusion, the anti-inflammatory and antioxidative properties of EPA may make it an effective therapeutic strategy for adverse cardiac remodeling associated with CRP overexpression.     

Exendin-4 improves cardiac function in mice overexpressing monocyte chemoattractant protein-1 in cardiomyocytes

The incretin hormone glucagon-like peptide-1 (Glp1) is cardioprotective in models of ischemia-reperfusion injury, myocardial infarction and gluco/lipotoxicity. Inflammation is a factor in these models, yet it is unknown whether Glp1 receptor (Glp1r) agonists are protective against cardiac inflammation. We tested the hypothesis that the Glp1r agonist Exendin-4 (Ex4) is cardioprotective in mice with cardiac-specific monocyte chemoattractant protein-1 overexpression. These MHC-MCP1 mice exhibit increased cardiac monocyte infiltration, endoplasmic reticulum (ER) stress, apoptosis, fibrosis and left ventricular dysfunction. Ex4 treatment for 8 weeks improved cardiac function and reduced monocyte infiltration, fibrosis and apoptosis in MHC-MCP1 mice. Ex4 enhanced expression of the ER chaperone glucose-regulated protein-78 (GRP78), decreased expression of the pro-apoptotic ER stress marker CCAAT/-enhancer-binding protein homologous protein (CHOP) and increased expression of the ER calcium regulator Sarco/Endoplasmic Reticulum Calcium ATPase-2a (SERCA2a). These findings suggest that the Glp1r is a viable target for treating cardiomyopathies associated with stimulation of pro-inflammatory factors.     

Regulatory T cells ameliorate cardiac remodeling after myocardial infarction

Persistent inflammatory responses participate in the pathogenesis of adverse ventricular remodeling after myocardial infarction (MI). We hypothesized that regulatory T (Treg) cells modulate inflammatory responses, attenuate ventricular remodeling and subsequently improve cardiac function after MI. Acute MI was induced by ligation of the left anterior descending coronary artery in rats. Infiltration of Foxp3(+) Treg cells was detected in the infarcted heart. Expansion of Treg cells in vivo by means of adoptive transfer as well as a CD28 superagonistic antibody (JJ316) resulted in an increased number of Foxp3(+) Treg cells in the infarcted heart. Subsequently, rats with MI showed improved cardiac function following Treg cells transfer or JJ316 injection. Interstitial fibrosis, myocardial matrix metalloproteinase-2 activity and cardiac apoptosis were attenuated in the rats that received Treg cells transfer. Infiltration of neutrophils, macrophages and lymphocytes as well as expression of tumor necrosis factor (TNF)-α and interleukin (IL)-1β were also significantly decreased, and the CD8(+) cardiac-specific cytotoxic T lymphocyte response was inhibited. Expression of interleukin (IL)-10 in the heart, however, was increased. Additional studies in vitro indicated that Treg cells directly protect neonatal rat cardiomyocytes against LPS-induced apoptosis, and this protection depends on the cell-cell contact and IL-10 expression. Furthermore, Treg cells inhibited proinflammatory cytokines production by cardiomyocytes. These data demonstrate that Treg cells serve to protect against adverse ventricular remodeling and contribute to improve cardiac function after myocardial infarction via inhibition of inflammation and direct protection of cardiomyocytes.     

Bacterial DNA induces myocardial inflammation and reduces cardiomyocyte contractility: role of toll-like receptor 9

AIMS: Myocardial function is severely compromised during sepsis. Several underlying mechanisms have been proposed. The innate immune system, i.e. Toll-like receptor (TLR) 2 and 4, significantly contributes to cardiac dysfunction. Little is known regarding TLR9 and its pathogenic ligand bacterial DNA in the myocardium. We therefore studied the role of TLR9 in myocardial inflammation and cardiac contractility. METHODS AND RESULTS: Wild-type (WT, C57BL/6) and TLR9-deficient (TLR9-D) mice and isolated cardiomyocytes were challenged with synthetic bacterial DNA (CpG-ODN). Myocardial contractility as well as markers of inflammation/signalling were determined. Isolated cardiomyocytes incorporated fluorescence-marked CpG-ODN. In WT mice, CpG-ODN caused a robust response in hearts demonstrated by increased levels of tumour necrosis factor (TNF-alpha), interleukin (IL)-1beta, IL-6, inducible nitric oxide synthase (iNOS), and nuclear factor kappaB activity. This inflammatory response was absent in TLR9-D mice. Under similar conditions, contractility measurements of isolated ventricular cardiomyocytes demonstrated a TLR9-dependent loss of sarcomeric shortening after CpG-ODN exposure. This observation was iNOS dependent as the application of a specific iNOS inhibitor reversed sarcomeric shortening to normal levels. CONCLUSION: Our data suggest that bacterial DNA contributes to myocardial cytokine production and loss of cardiomyocyte contractility via TLR9.     

Toll-like receptor 4 induced FcgammaR expression potentiates early onset of joint inflammation and cartilage destruction during immune complex arthritis: Toll-like receptor 4 largely regulates FcgammaR expression by interleukin 10

OBJECTIVE: To study the role of Toll-like receptor (TLR)2 and 4 in the onset of joint inflammation and cartilage destruction during immune complex-mediated arthritis (ICA), and its relationship with FcgammaR expression. MATERIALS AND METHODS: ICA was induced in knee joints of TLR2-/- and TLR4-/- mice and their wild-type controls. Joint inflammation and cartilage destruction were measured in the knee joint using histology. mRNA levels were determined in synovial specimens and macrophages using quantitative polymerase chain reaction and cytokine protein levels in synovial washouts using Bioplex. RESULTS: Joint inflammation and cartilage destruction were not different in arthritic TLR2-/- and wild-type mice. By contrast, at day 1 after ICA induction, joint swelling and proteoglycan depletion in knee joints of TLR4-/- mice were considerably lower (inflammation 68-79% and proteoglycan depletion 27-76%) when compared with wild-type controls. Cytokine production at this time point was markedly reduced in TLR4-/- mice (interleukin (IL)1, IL6, macrophage inflammatory chemokine (MIP)-1alpha and keratinocyte-derived chemokine 49%, 72%, 68% and 84%, respectively). In arthritic synovia of TLR4-/- mice, and also after injection of the antigen poly-l-lysine (PLL) lysozyme alone, mRNA levels of FcgammaR, and the FcgammaR regulating cytokine IL10 were considerably lower. Stimulation of peritoneal macrophages with PLL lysozyme up regulated mRNA levels of FcgammaR and IL10, whereas neutralisation by anti-IL10 antibodies largely blocked FcgammaR up regulation. At day 4, joint inflammation and cartilage destruction were comparable in TLR4-/- mice and wild-type controls. CONCLUSION: TLR4 regulates early onset of joint inflammation and cartilage destruction during ICA arthritis by up regulation of FcgammaR expression and enhanced cytokine production. TLR4-mediated up regulation of FcgammaR is largely mediated by IL10.     

补体5a受体在阿霉素致急性心力衰竭心肌损伤的早期研究

目的:探讨补体系统补体5a受体(complement 5a receptor,C5aR)在急性心力衰竭(心衰)早期,对心脏功能影响以及对心肌损伤的作用。方法:选择12 w龄C57BL/6J野生型及C5aR敲除小鼠各12只,分别随机分为野生小鼠对照组、野生小鼠心衰组、C5aR敲除小鼠对照组和C5aR敲除小鼠心衰组等共4组,每组6只。采用单次腹腔注射阿霉素20 mg/kg建立小鼠急性心衰模型,对照组采用同计量0.9%氯化钠液注射;阿霉素注射3d后显微超声检测小鼠心室射血分数和短轴缩短率,处死后测量体质量以及心脏质量;运用半定量PCR、蛋白印迹技术Western Blotting、免疫荧光等实验方法观察C5aR在野生小鼠心脏中的表达。C5aR敲除小鼠心脏组织采用HE染色观察心肌形态、Masson染色观察心肌纤维化程度,WGA染色观察心肌横截面大小,免疫组化染色观察转化生长因子-β(TGF-β)及α-平滑肌肌动蛋白(α-SMA)在心脏中表达。结果:与野生小鼠对照组相比,野生小鼠心衰组中C5aR的mRNA及蛋白表达均显著上调(P<0.05);与野生小鼠心衰组相比,C5aR敲除小鼠心衰组体质量及血压均显著升高(均为P<0.05),心室射血分数和短轴缩短率均显著升高(均为P<0.05),C5aR敲除小鼠心衰组胶原沉积及α-SMA表达均显著降低(均为P<0.05),TGF-β表达显著降低(P<0.01)。结论:C5aR在阿霉素诱导心衰模型中表达上调、加重了心肌损伤且促进了心脏纤维化,而C5aR敲除保护小鼠心功能并抑制纤维化,提示C5aR在小鼠急性心衰早期具有促进心脏纤维化作用。     

Myocardial Regulation of p300 and p53 by Doxorubicin Involves Ubiquitin Pathways

Background Doxorubicin (Dox) depletes p300 from cardiac myocytes and induces apoptosis of these cells. p300 protein possesses ubiquitin ligase activity for the p53 tumor suppressor gene product, catalyzes p53 polyubiqutination, and facilitates p53 degradation in an ubiquitin-dependent manner. The present study investigated the ubiquitin-dependent regulation of p53 by Dox and p300 in cardiac myocytes. Methods and Results Primary cardiac myocytes from neonatal rats were exposed to a proteasome inhibitor, MG132, in culture. MG132 increased both p300 and p53 protein levels in these cells, suggesting that ubiquitin-dependent degradation is involved in the homeostasis of these proteins. Notably, treatment of cardiac myocytes with Dox decreased the protein levels of p300 but markedly increased those of p53. By immunoprecipitation-Western blotting, it was shown that treatment with Dox decreased poly-ubiquitinated p53 but increased that of p300 in cardiac myocytes. Finally, the overexpression of p300 in cardiomyocytes suppressed the Dox-mediated increase in the p53 level in addition to inhibiting Dox-induced apoptosis. Conclusion Dox reciprocally regulates p300 and p53 through ubiquitin-dependent pathways and that p300, by its ubiquitin ligase activity, is partially involved in the ubiquitin-dependent degradation of p53 in cardiac myocytes. (Circ J 2008; 72: 1506 - 1511).     

PTEN-inducible kinase 1 (PINK1)/Park6 is indispensable for normal heart function

Oxidative stress is caused by an imbalance between reactive oxygen species (ROS) production and the ability of an organism to eliminate these toxic intermediates. Mutations in PTEN-inducible kinase 1 (PINK1) link mitochondrial dysfunction, increased sensitivity to ROS, and apoptosis in Parkinson's disease. Whereas PINK1 has been linked to the regulation of oxidative stress, the exact mechanism by which this occurs has remained elusive. Oxidative stress with associated mitochondrial dysfunction leads to cardiac dysfunction and heart failure (HF). We hypothesized that loss of PINK1 in the heart would have deleterious consequences on mitochondrial function. Here, we observed that PINK1 protein levels are markedly reduced in end-stage human HF. We also report that PINK1 localizes exclusively to the mitochondria. PINK1(-/-) mice develop left ventricular dysfunction and evidence of pathological cardiac hypertrophy as early as 2 mo of age. Of note, PINK1(-/-) mice have greater levels of oxidative stress and impaired mitochondrial function. There were also higher degrees of fibrosis, cardiomyocyte apoptosis, and a reciprocal reduction in capillary density associated with this baseline cardiac phenotype. Collectively, our in vivo data demonstrate that PINK1 activity is crucial for postnatal myocardial development, through its role in maintaining mitochondrial function, and redox homeostasis in cardiomyocytes. In conclusion, PINK1 possesses a distinct, nonredundant function in the surveillance and maintenance of cardiac tissue homeostasis.